The present invention relates to an electronic flow meter, and in particular, to an electronic flow meter for magnetically detecting a rotational frequency of a rotator rotating according to a flow rate of a fluid.
An electronic flow meter utilizing a magnetic sensor has lately been adopted for a water meter, and so forth. In the case where the electronic flow meter is adopted for the water meter, and so forth, it is difficult to supply power from outside, and therefore, a battery is generally used as a power source. For this reason, with the electronic flow meter, it is necessary to restrain an amount of current consumed in order to extend the service life of the battery.
The electronic flow meter, however, detects a flow rate of a fluid, and a flow direction of the fluid (a normal/reverse direction in which a rotator of the magnetic sensor is rotated) according to first and second signals outputted from the magnetic sensor, respectively. For this reason, the electronic flow meter has a need for causing the first and second signals outputted from the magnetic sensor, respectively, to respond quickly to a rotational speed of the magnetic sensor, and current is therefore supplied to the magnetic sensor at all times, so that the amount of current consumed has increased.
Accordingly, with the electronic flow meter disclosed in Japanese Unexamined Patent Publication No. Hei10 (1998)-246662, a cycle of sampling first and second signals outputted from the magnetic sensor, respectively, is varied according to a flow rate in stages of a low speed, an intermediate speed, and a high speed, and the magnetic sensor is intermittently supplied with current in such a way as to match variation in the cycle of sampling, thereby causing a decrease in current consumption.